#! /bin/bash
#
# Translates an existing AWS Route53 zone into Terraform `aws_route53_record` resources.
#
# Released under the MIT license; YMMV. Tested on Linux with:
#
# - jq-1.6
# - terraform v0.12.26
# - aws-cli/1.17.14
#

# The base filename for both the TF resources and the import script
OUTNAME=route53_records

# Your AWS Zone ID
ZONE_ID=ABC123

# The Terraform variable to reference in aws_route53_record entries
ZONE_VAR=aws_route53_zone.MY_RESOURCE.zone_id


as_tf_route53_record_dns_name() {
  local name="$1"

  echo $name | sed 's/\\052/*/'
}

as_tf_route53_record_resource_name() {
  local name="$1"
  local type=$2

  echo $name | grep -i '^[a-z_]' > /dev/null || {
    # Terraform requires resource names to start with an alpha character or
    # underscore. This one didn'ts, but we can fix that.
    name="_${name}"
  }

  echo "$(echo $name | tr '.' '-' | sed 's/\\052/wildcard/')$(echo $type | tr '[:upper:]' '[:lower:]')"
}

as_tf_route53_alias() {
  local alias=$1

  cat <<EOF
  alias {
      zone_id                = $(echo "$alias" | jq .HostedZoneId)
      name                   = $(echo "$alias" | jq .DNSName)
      evaluate_target_health = $(echo "$alias" | jq -r .EvaluateTargetHealth)
    }
EOF
}

as_tf_route53_record() {
  local json="$1"
  local name=$(echo "$json" | jq -r .Name)
  local type=$(echo "$json" | jq -r .Type)
  local alias=$(echo "$json" | jq -r .AliasTarget)

  cat <<EOF
resource "aws_route53_record" "$(as_tf_route53_record_resource_name $name $type)" {
  zone_id = ${ZONE_VAR}
  name    = "$(as_tf_route53_record_dns_name $name)"
  type    = "${type}"
  $(
    if [[ "$type" == "A" && "$alias" != "null" ]]; then
      as_tf_route53_alias "$alias"
    else
      echo "ttl     = $(echo "$json" | jq -r .TTL)"
      echo "records = $(echo "$json" \
        | jq -r --indent 4 '.ResourceRecords | map(.Value)' \
        | sed 's/\\"//g' | sed 's/",*$/",/')"
    fi
  )
}
EOF
}

as_tf_route53_record_import() {
  local json="$1"
  local name=$(echo "$json" | jq -r .Name)
  local type=$(echo "$json" | jq -r .Type)

  local import_id=${ZONE_ID}_$(echo "$name" | sed 's/\.$//')_${type}

  echo "terraform import aws_route53_record.$(as_tf_route53_record_resource_name $name $type) $import_id"
}

rm ${OUTNAME}.txt
rm ${OUTNAME}_import.sh

echo '#!/bin/sh
' > ${OUTNAME}_import.sh

chmod +x ${OUTNAME}_import.sh

aws route53 list-resource-record-sets \
  --hosted-zone-id=$ZONE_ID \
  | jq -c '.ResourceRecordSets[]' \
  | while IFS= read -r line
do
  as_tf_route53_record "$line" >> ${OUTNAME}.txt
  as_tf_route53_record_import "$line" >> ${OUTNAME}_import.sh
done

echo "Zone retrieved from Route 53!"
echo
echo "Copy the resources from ${OUTNAME}.txt into main.tf, then import existing"
echo "records using:"
echo
echo "    $ ./${OUTNAME}_import.sh"
echo